In-vivo temperature imaging refers to temperature imaging of tissues of a complete and survival individual. In the biomedical field such as hyperthermia cancer therapy, as it is so difficult to obtain temperature field distribution information in vivo accurately that many medical treatments cannot be used effectively. At present, in-vivo temperature measurement is categorized as invasive measurement and non-invasive measurement. Invasive measurement is simple and is able to monitor temperature of a lesion directly with high accuracy in real time. However, it is highly traumatic, the probe insertion tends to cause transfer of infected cells, the radiation of a heating source have affect on the probe directly may leading to decrease of measuring accuracy, and the measured temperature data is a point temperature which cannot construct temperature field distribution of the whole lesion. Meanwhile, non-invasive measurement can avoid wound infection or proliferation of cancer cells effectively and realize real-time imaging of an in-vivo temperature field with comparatively high accuracy, which enables it to have widely potential applications in the biomedical field.
Non-invasive measurement mainly includes infrared temperature measurement, ultrasonic temperature measurement, NMR temperature measurement and magnetic nanoparticle remote temperature measurement. Infrared temperature measurement measures temperature of a measured object according to infrared radiation intensity thereof, which is applicable for surface temperature measurement of objects instead of temperature field measurement deeply in tissues, and is vulnerable to emissivity of an object and aerosol particles. The key of ultrasonic temperature measurement is to measure propagation time of an ultrasonic accurately, which requires to measure acoustic characteristics and temperature characteristics of tissues in advance. However, temperature characteristics of tissues are instable and differ greatly therebetween, which affects temperature measurement significantly. NMR temperature measurement features high price and limited space resolution and temperature resolution, and is unfavorable for widespread applications. Non-invasive temperature field imaging by magnetic nanoparticles may overcome the above shortcomings, by which in-vivo temperature imaging may be realized thereby monitoring a hyperthermia cancer therapy process in real-time so as to make adjustments timely and effectively.
However, current non-invasive in-vivo temperature measurement method based on magnetic nanoparticles can only realize single-point temperature measurement instead of obtaining temperature field distribution deeply in tissues. Besides, accuracy of temperature measurement is affected by concentration distribution of magnetic nanoparticles deeply in tissues. Therefore, it is an urgent problem to be resolved in the field of magnetic nanoparticle hyperthermia cancer therapy that developing a method capable of realizing in-vivo temperature field imaging without knowing concentration distribution of magnetic nanoparticles.